Valve train units that include double-shaft camshafts, as well as camshaft adjusters for these valve train units, are also known from the prior art. For example, DE 10 2008 023 098 A1 provides a double pivotably rotatable camshaft adjuster in a layered design, and a valve train assembly of an internal combustion engine with a camshaft and this type of camshaft adjuster, for changing the relative position of the camshaft with respect to a second shaft, such as a crankshaft or drive shaft. The camshaft adjuster, as a rotary component, includes at least one rotor and one stator, which between them enclose hydraulic chambers with changeable, in particular oppositely directed, volumes. At least one of the rotary components is connected to the camshaft, via a pin that engages with the camshaft, in such a way that changes in position of the rotor with respect to the stator are transmitted via the pin to the camshaft.
In other words, adjusters/camshaft adjusters are thus already known whose stator is driven by a gearwheel and supported on the inner camshaft, and fixedly mounted via a rotor. However, with some designs it has proven disadvantageous that the inner camshaft (inner shaft) is generally relatively difficult to center and to support, since the inner camshaft is usually supported by the connecting element, designed as a transverse pin, via the outer cam. For these reasons, it is not possible to manufacture the inner camshaft with great precision. This is disadvantageous in particular for designs in which the gearwheel is provided above the adjuster, and in addition gearwheel runout tolerances must be taken into consideration for the required function. In known approaches such as in DE 10 2011 120 815 A1, even two gearwheels are thus necessary, which, however, in turn adversely affect the number of components and the manufacturing costs for the camshaft adjuster and the valve train assembly/valve train unit. In addition, manufacturing the camshaft end in each case, in particular the inner shaft (by expansion), is relatively complicated.
Further prior art is also known from DE 10 2011 078 818 A1.